117 lines
2.8 KiB
C
117 lines
2.8 KiB
C
#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdint.h>
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#define ISDIGIT(c) (c >= 0x30 && c <= 0x39)
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inline uint64_t parse_number(const char *line, ssize_t j);
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int main(int argc, char **argv) {
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FILE *input;
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char *line = NULL;
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size_t line_length = 0;
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if (argc == 1 || argv[1][0] == '-')
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input = stdin;
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else if ((input = fopen(argv[1], "r")) == NULL) {
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fprintf(stderr, "Cannot open file %s\n", argv[1]);
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return -1;
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}
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char **engine = NULL;
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ssize_t engine_line_size = 0;
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ssize_t engine_lines = 0;
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while (getline(&line, &line_length, input) != -1) {
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ssize_t len = strlen(line)-1;
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if (engine == NULL) {
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engine = (char **) calloc(len, sizeof(char*));
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engine_line_size = len;
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}
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engine[engine_lines] = (char*) calloc(len, sizeof(char));
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memcpy(engine[engine_lines], line, len);
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++engine_lines;
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memset(line, 0, line_length);
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}
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uint64_t part_number = 0;
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for (ssize_t i = engine_lines-1; i >= 0; --i)
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for (ssize_t j = engine_line_size-1; j >= 0; --j) {
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if (engine[i][j] != '*')
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continue;
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uint64_t n = 1;
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int8_t p = 0;
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if (ISDIGIT(engine[i][j+1])) {
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n *= parse_number(engine[i], j+1);
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p++;
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}
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if (ISDIGIT(engine[i][j-1])) {
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n *= parse_number(engine[i], j-1);
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p++;
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}
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if (ISDIGIT(engine[i+1][j])) {
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n *= parse_number(engine[i+1], j);
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p++;
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} else {
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if (ISDIGIT(engine[i+1][j+1])) {
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n *= parse_number(engine[i+1], j+1);
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p++;
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}
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if (ISDIGIT(engine[i+1][j-1])) {
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n *= parse_number(engine[i+1], j-1);
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p++;
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}
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}
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if (ISDIGIT(engine[i-1][j])) {
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n *= parse_number(engine[i-1], j);
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p++;
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} else {
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if (ISDIGIT(engine[i-1][j+1])) {
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n *= parse_number(engine[i-1], j+1);
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p++;
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}
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if (ISDIGIT(engine[i-1][j-1])) {
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n *= parse_number(engine[i-1], j-1);
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p++;
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}
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}
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if (p >= 2)
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part_number += n;
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}
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for (ssize_t i = 0; i < engine_lines; ++i)
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free(engine[i]);
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free(engine);
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printf("%lu\n", part_number);
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return 0;
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}
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inline uint64_t parse_number(const char *line, ssize_t j) {
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uint64_t n = 0;
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uint64_t multiplier = 1;
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while (ISDIGIT(line[j+1])) j++;
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while (ISDIGIT(line[j])) {
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n += (line[j]&0xf) * multiplier;
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multiplier *= 10;
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j--;
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}
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return n;
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} |